Google says 170m people have registered for its Google+ service since it was launched 10 months ago – and that 100m have "engaged" with the service at least once in the past 30 days and 50m have engaged with the service at least once a day in the past month.

The announcement came as the company revealed a facelift for the service, which it billed as being a means of making "sharing more awesome" with functionality for full-size photos, videos, a new "navigation ribbon" and "conversation cards" allowing users to dip in and out of chats with their circles of friends, family and business contacts.

The "hangout" feature, which lets people create ad-hoc video chats, is more prominent, with its own dedicated page.

A makeover so soon after launch is not surprising for Google, whose philosophy is all about iterative change.

But it will intensify the spotlight on the company's battle to take on Facebook, which dominates social networking with more than 850m users.

Since January, new users signing up for Google services such as a YouTube or Gmail account have had to create a Google+ profile: in the past three months, that has added 80m people, says Search Engine Watch. In all, Gmail has 350m users worldwide.

There is widespread industry suspicion that many of those who are classified by Google in its blogpost about the revision as having "upgraded" to Google+ had a look at the service and not returned, depressing frequency of use figures. Other studies have suggested that people use the service for far less time than other services: a ComScore study released in February found that users spent an average of just three minutes on Google+ in the entire month of January - far behind Facebook, which consumed 18% of peoples' entire time online for January. Pinterest, Twitter and LinkedIn all saw more visitors who spent longer on the sites, ComScore said.

Senior vice president Vic Gundotra says in the company's official blog that the new design will create "a more functional and flexible version of Google+" and will be rolled out over the next few days.

He added: "We think you'll find it easier to use and nicer to look at, but most importantly, it accelerates our efforts to create a simpler, more beautiful Google.

"Simply put, we're hoping to make sharing more awesome by making it more evocative. You know that feeling you get when a piece of art takes your breath away, or when a friend stops by with unexpected gifts? We want sharing to feel like that, every single time," said Gundotra.

In the US, Google has pushed Google+ profiles into search results - with the effect that a search for "Mark Zuckerberg" puts his Google+ page ahead of his Facebook page, a result which appeared distorted compared with previous Google search results. That drew protests from Twitter, Facebook and MySpace in January; a number of engineers from the three companies launched a plugin called "Don't Be Evil" to roll back its effects. However, it has not extended the changed search profile to Europe, where it is the subject of an antitrust investigation by the European commission, which could yet take further action.

Initial reaction on Twitter was cynical. "Oooh, Google+ had a new look. How exciting. Now back to ignoring it." wrote Pablo Elizalde.

Mark Wilson, at Fastcodesign, noted: "Google+ has failed to take off. And it's not even necessarily a fault of the product: Facebook is the de facto social network of our time. If there's a second in command, it's the more quick and casual Twitter. There are only so many social networks that we can all be social on every day."

Other users have complained that because Google+ does not offer an API, there is no way to automatically upload content: any new post or "+1" of a post requires the user to log in, thus boosting the apparent user numbers. By contrast, Facebook and Twitter offer comprehensive APIs so that users can add content from a variety of apps and third-party systems.